Transmitter



Patented Aug. 8, 1922.

nurse stares eras res.

THOMAS A. EDISON, F LLEWELLYN PARK, WEST ORANGE, NEW JEY.

TRANSMITTER.

Specification of Letters Patent.

Patented Aug. d, 1922.

To all whom it may concern:

Be it known that I, THoMAsA. EDISON, a citizen of the United States, andaresident of Llewellyn Park, West Orange, Essex County, New Jersey, haveinvented certain new and useful Improvements in Transmitters, of whichthe following is a description.

My invention ,relates to transmitters, and more particularly tomicrophone transmitters wherein the desired variations in current areproduced by variations in electrical resistance caused by varying thepressure upon a quantity of granular conductive material, such ascarbon, which is disposed be tween electrodes in the circuit carryingthe current, preferably in Va somewhat loose state, the requisitechanges in pressure be ing efiected between the electrodes and thegranular material by a diaphragm or other means adapted to be set intovibration b the sound waves from a source of soun such as the humanvoice.

Practically all microphone transmitters of this type such as are nowused are seriously and adversely affected by phenomena extraneous to thesounds which the same are designed to transmit, such for example,.as

' shocks, jars, vibrations, concussions, etc. oc-

curring in the neighborhood thereof, these phenomena often causing suchrelative movement of the conductive granules disposed between theelectrodes of the microphone transmitter as to produce extraneous orforeign sounds loud enough when amplified to practically obliterate andrender .it impossible to understand or detect the sounds which themicrophone is intended powerful amplifying devices, such as the tionwill be hereinafter more fully deto transmit.

The principal object of my invention is audion, with the transmitter.

More specifically described, my invention consists in supporting amicrophone transmitter entirely by a mass or masses of resilia entmaterial, preferablythe material known by the trade name rubber spongeThe mounting of the transmitter in this manner prevents a majority ofall of the stresses,

jars, etc. of the building, vehicle or other structure in which themicrophone may be located from being communicated thereto and theproduction thereby of any appreciable internal movements in the mass ofconductive granules or fine particles. The invention also consists inmaking still further provision against the production of internalmovements in the mass of conductive ,granules of the microphone by jars,etc., preferably by filling the space between-the electrodes in whichthese granules are disposed with a very light hydrocarbon oil,preferably pure distilled motor gasolenehaving a very low boiling pointwhereby the loose mass of granules or fine particles of conductivematerial will be completely immersed therein. The effect of this liquidis to dampen the movement of the conductive granules and probably holdthem in closer contact. Thisliquid also acts by its buoyancy to lightenthe pressure of the granules on each other. I find that thesensitiveness of the microphone to the sounds which it is desired totransmit thereby and which are communicated to the main diaphragm of themicrophone by the air or other fluid in which the latter is-disposed, isbut ver slightly diminished by the use of the liqui while internalmovements of the mass of conductive granules or fine particles by jars,etc. occurring in the vicinity of the microphone, and thereby theproduction of jar or like extraneous sounds in the microphone, arepractically eliminated. A microphon apparatus in which the features justdescribed are combined is extremely efli'cient, as it is possible totransmit thereby very clearly and distinctly, sounds of the weakestcharacter as well as loud sounds; my improved .mircrophonic apparatusbeing especially adapted for the transmission of oral communications, asthe articulation and distinctness of such communications transmittedthereby are greatly increased.

Other objects and features of my inven- 40 Y 1 ed thereon. A hollow neck13 extends cen-' .tire support for the" microphone, and prevents-nearlyall. jars,etc. to Which the base is subjected from being communicated tothe transmitter.

The microphone casing consists of ametallic sound box 4 having an archedbody porvmounted on the said seat.

tion from which extends an annular flange 5, and a cover 6 provided witha peripheral flange the endjportion of which surrounds the flange 5 andis detachably secured thereto in any suitable manner. The sound box 4 isprovided with an annular seat 7 about the arched body portion thereof,and a metallic diaphragm 8, is suitably secured against an annularshellaced fabric ring 9 The peripheral edge portion of the diaphragm 8preferably has applied thereto a ring 10 formed of rubber or othersuitable yielding material, covering both faces of such edge portion,and the diaphragm is preferably held to its seat by means 0 a pluralityof leaf springs 11 secured at one end tolthe annular flange 5 of thesound box and bearing attheir free ends on the rubber ring 10, said freeends preferably having sleeves 12 of soft rubber or other suitableyielding material mounttrally from the base of the sound box 4 and 'isadapted to have a; horn or other suitable receiver secured thereto bymeans of which the sound waves from the person speaking, or other sourceof sound, are caused to converge into thesound box body. and set thediaphragm 8 into vibration. A bridge 15 extends diametrically across thesound box body and has its ends suitably secured to the annular flange 5as by means of screws; 16, the central portion of this bridge beingprovided with a U-shaped ortion 17 extending tdwards the cover 6.eference character 18 represents a cylindrical bearing member or sleevewhich extends through an opening in the center of the cover 6 in linewlth the hollow neck 13 of the sound box 4, the outer end of said sleevebeing provided with an annular flange 19 and the inner end thereof beingprovided with a redu d cylindrical portion 20 which extends through anopening provided in the center of the U-shaped pdrtion" 17 of bridge 15.The inner end of the reduced portion 20 of'the sleeve 18 has a nut 21threaded thereon, whereby the sleeve 18 is rigidly secured to the bridge15.

An arm 22 constituting a contact member is mounted on the reduced endportion'20 of sleeve 18 between the shoulder. provided by such reducedportion and the base of the U- shaped portion 17 of bridge 15, andsuitable insulation 23 separates the base of the U- shaped portion 17from the arm or contact member 22, the sleeve 18 and the 'nut 21.

A cylindrical rod or stem 24 is slidably mounted in and extends throughthe bearin member or sleeve 18, rotary movement 0 this rod beingprevented by means of a pin 25 secured to the sleeve 18 and projectinginto a longitudinal slot 26 formed in the rod. The inner end of rod 24.has rigidly secured thereto and preferablyv formed integrally therewitha'cup-shaped member 27 which constitutes areceptacle or chamber in whicha pair of spaced electrodes E and a mass of conductive granules or veryfine particles 28, preferably of carbon, are disposed. The end ofthischamber is closed by a mica diaphragm 29 which is held in place by aring 30 threaded on the cu -shaped member 27. The spaced electrodes l)of the transmitter arerespectively disposed between the mass ofconductive granules 28 and the diaphragm 29 and the base of member 27. Asmall conical metallic member 31 is disposed between the diaphragms 8and 29 and is pro-' vided at one end with a metallic button 32 whichextends through and is rigidly connected with the diaphragm 8 at thecenter thereof, and is suitably mechanically and electrically connectedat its other end with the diaphragm29.

the electrode E adjacent A quantity of liquid L, such as a lighthydrocarbon oil, preferably pure distilled motor gasolene having a verylow boiling point, is inserted in the cup-shaped member or receptacle 27with the granular carbon 28, a sufficient volume of such li uidpreferably being employed to substantially fill all the space in suchreceptacle between the electrodes E not occupied by the loose mass offine particles of carbon. .It will thus be apparent that the loose massof fine particles or granules of carbon is completely immersed in thelight hydrocarbon oil. The results arisin from the use of this liquidhave already -been fully described. A disc 33 having a knurled head 34is threaded on the outer end of the rod or stem 24 and bears against theouter face of the, flange 19 of the sleeve or bearing member 18.x Amem-.

ber 35 is secured 'at one'end to the flange 19, as by a screw 36, andthe other end thereof is provided with a finger 37 which projects intoan annular groove 38 formed in the disc 33, whereby movement of thelatter axially of the member or sleeve 18 is prevented. It

willl thus' be see n that the turning of disc 33 will effect slidingmovement of the" rod or stem 24 in the sleeve 18, and therefore movementof the cup-shaped member or receptacle 27 axially of the microphonecasing. As the member 31 connects the diaphragm 29 andadjacentnelectrode E with the diaphragm 8mounted on the soundbox 4, itwill be seen that such movement of the member 27 may be utilized for theadjustment of the initial pressure on the mass'of granular carbon 28 tosuit varying conditions of use. The face of the disc 33 is preferablyprovided with a scale or graduations 39 with which a suitable index orpointer 41, formed on the end-of a member 40 se'-' cured to the flange19, co-operates-to facilitate such adjustment.

A. contact member 42 is suitably secured to the bridge 15 and separatedtherefrom by suitable insulation 43, and a flexible conductor 44connects this contact member with the conical metallic member 31.Conductors 45 and 46 respectively connected to the contact members 22and 42, as by binding screws 47 and 48, extend from the microphonethrough a suitable opening 49 in the cover 6 for connection in thecircuit.

The path of the circuit through the mi- 'crophone is as follows: Fromthe conductor 45 through contact member 22, sleeve 18, rod 24, to thebase of the cup-shaped member 27 and the adjacent electrode E, thenthrough the granular carbon 28, the other electrode E,member 31,conductor 44, contact member 42, to the other conductor 46.

While I have shown the preferred embodiment of my invention, it is to beunderstood that the same is subject to numerous changes. andmodifications without any departure from the spirit of the invention andthe scope of the appended claims. 7

Having now described my invention, what I claim as new and desire toprotect by Letters Patent is as follows 1. A microphone transmittercomprising a pair of spaced electrodes, and a loose mass of fineparticles or granules of conductive material wholly immersed in a singleliquid between said electrodes, substantially as described.

of October, 1918.

2. A microphone transmitter comprising a air of spaced electrodes, and aloose mass 0 fine particles or granules of conductive material whollyimmersed in aliquid hydrocarbon between .said electrodes, substantiallyas described.

3. A microphone transmitter comprising a pair of spaced electrodes, anda loose mass of fine particles or granules of conductive material whollyimmersed in gasolene between said electrodes, substantially asdescribed.

4. A. microphone transmitter comprising a fluid-tight receptacle filledwith a single liquid and carrying a pair of spaced electrodes, and aloose mass'of fine particles or granules of conductive material whollyimmersed in said liquid between said electrodes, substantially asdescribed.

5. A microphone transmitter comprising a fluid-tight receptacle filledwith a liquid hydro-carbon and carrying a pair of spaced electrodes, anda loose mass of fine particles or granules of conductive material whollyimmersed in said liquid between said electrodes, substantially asdescribed.

6. In combination, a microphone transmitter comprising a pair of spacedelectrodes and a loose mass of fine particles or granules of conductivematerial wholly immersed in a single liquid between saidelectrodes, anda large mass of rubber sponget in which said microphone transmitter ismounted and by which it is wholly and directly supported, substantiallyas described.

7 In combination, a microphone transmitter comprising a pair of spacedelectrodes and a loose mass of fine particles or granules of conductivematerial wholly immersed in a body or liquid hydro-carbon between saidelectrodes, and a large mass of rubber like material in which saidmicro-.

phone'transmitter is mounted and by which it is wholly and directlysupported, substantially as described.

This specification signed this 23rd day rnos. a. unison;

